These test methods cover procedures for determining the mean grain size, and the distribution of grain intercept lengths or grain areas, for polycrystalline metals and nonmetallic materials with equiaxed or deformed grain shapes, with uniform or duplex grain size distributions, and for single phase or multiphase grain structures.

The measurements are performed using semiautomatic digitizing tablet image analyzers or automatic image analyzers. These devices relieve much of the tedium associated with manual measurements, thus permitting collection of a larger amount of data and more extensive sampling which will produce better statistical definition of the grain size than by manual methods.

The precision and relative accuracy of the test results depend on the representativeness of the specimen or specimens, quality of specimen preparation, clarity of the grain boundaries (etch technique and etchant used), the number of grains measured or the measurement area, errors in detecting grain boundaries or grain interiors, errors due to detecting other features (carbides, inclusions, twin boundaries, and so forth), the representativeness of the fields measured, and programming errors.

Results from these test methods may be used to qualify material for shipment in accordance with guidelines agreed upon between purchaser and manufacturer, to compare different manufacturing processes or process variations, or to provide data for structure-property-behavior studies.

1. Scope

1.1 These test methods are used to determine grain size from measurements of grain intercept lengths, intercept counts, intersection counts, grain boundary length, and grain areas.

1.2 These measurements are made with a semiautomatic digitizing tablet or by automatic image analysis using an image of the grain structure produced by a microscope.

1.3 These test methods are applicable to any type of grain structure or grain size distribution as long as the grain boundaries can be clearly delineated by etching and subsequent image processing, if necessary.

1.4 These test methods are applicable to measurement of other grain-like microstructures, such as cell structures.

1.5 This standard deals only with the recommended test methods and nothing in it should be construed as defining or establishing limits of acceptability or fitness for purpose of the materials tested.

1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

1.7 The sections appear in the following order:

2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

ASTM Standards

E3 Guide for Preparation of Metallographic Specimens

E7 Terminology Relating to Metallography

E112 Test Methods for Determining Average Grain Size

E407 Practice for Microetching Metals and Alloys

E562 Test Method for Determining Volume Fraction by Systematic Manual Point Count

E883 Guide for Reflected-Light Photomicrography

E930 Test Methods for Estimating the Largest Grain Observed in a Metallographic Section (ALA Grain Size)

E1181 Test Methods for Characterizing Duplex Grain Sizes

E1245 Practice for Determining the Inclusion or Second-Phase Constituent Content of Metals by Automatic Image Analysis

Keywords

ALA grain size; anisotropy index; area fraction; ASTM grain size number; austenite grains; automatic image analysis; calibration; chord length; confidence level; digitizing tablet; duplex grain structures; equiaxed grains; etchant; ferrite grains; grain boundary; grains; grain size; intercept length; intersection count; magnification; non-equiaxed grains; polycrystalline; prior-austenite grain boundaries; relative accuracy; semiautomatic image analysis; skeletonization; standard deviation; twin boundary; watershed segmentation; ALA grain size; Anisotropy index; ASTM grain size number (G); Calibration--metals/alloys analysis instrumentation; Digitizing tablet; Duplex grain structures; Equiaxed grains; Etching (materials/process); Image analysis--metals/metallic materials; Intercept length/count; Metallographic analysis/inspection; Metals and metallic materials; Microscopic examination--metals/alloys; Microstructures; Nonequiaxed grains; Nonmetallic materials; Photomicrography; Polycrystalline materials; Semi-automated methods; Specimen preparation (for testing)--metals/alloys; Watershed segmentation;

ICS Code

ICS Number Code 19.120 (Particle size analysis. Sieving)

Citing ASTM Standards

[Back to Top]